ENGR-101 Week 02: Shutter Speed Measurement

Transcription

1 ENGR-101 Week 02: Shutter Speed Measurement

2 Today s Agenda 11:00 Role Call Welcoming Remarks Fun Motivation (Related YouTube Video) 11:15 Experiment 1: Extract camera flash circuit board 11:35 Experiment 2: Oscilloscope and FG setup: burst and trigger 11:55 Experiment 3: Camera flash circuit board installation 12:15 Experiment 4: Reading measurements (with cursors) 12:35 Discussion Points 13:00 Adjourn

3 Generation Gap: Class of 198X vs. Class of Terabyte World Atari 400 (16K) IBM XT (1 MB) Class of 1980x Megabyte Generation Pentium 3 (40 MB) Multicore (GB) Class of Gigabyte Generation Worldwide Optical Content Worldwide Printed Content US Broadcast Media Worldwide Film Content Internet Worldwide Magnetic Content World Telephone Calls Electronic Flow of New Info 103 TB 1,633 TB 14,893 TB 420,254 TB 532,897 TB 4,999,230 TB 17,200,000 TB 17, 903, 340 TB Giga = 10^6 Tera = 10^12 Peta = 10^15

4 Source: Hans Moravec When Will Computer Hardware Match the Human Brain, 1997

5 Biological evolution and human technology both show continual acceleration. The time between events continues to decrease; 2B years from the origin of life to cells and 14 years between the PC and World Wide Web.

6 2014: Getting Lost 2019: Libraries 2020: Copyright 2030: Keys 2033: Coins 2036: IC cars 2050+: Ugliness, Nation States, Death Source: What s Next and the Future Exploration Network

7 Erosion of Boundaries in the Information Age Between products and services: think cell phones Between producers and users: think social media Between IT, comm, media, consumer electronics: think Amazon Between IT and non-it industries: think Walmart Between academia, industry, disciplines, theory, applied research 48 years 34 years 4 years 1895: Heavier than air flying machines are impossible, Lord Kelvin 1943: I think there s a world market for maybe 5 computers, Thomas Watson 1977: There is no reason why anyone should have a PC in their home, Ken Olsen 1981: 640K ought to be enough for anyone, Bill Gates What can we expect in the next years? 2

8 Motivation for Today s Lab Bring camera: A disposable camera will be disassembled Search and read about disposable cameras Search how camera flashes work What are coil guns and tasers? What is a film ASA rating and how does this relate to shutter speed? Roughly calculate the shutter speed needed for a disposable camera

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10 Experiment 1: Extract camera flash circuit board Goal: Dissect disposable camera to extract flash circuit Step 1: Remove battery Pry apart front and back sides of casing Remove film Pry apart flash circuit board assembly ENGR Website: Extra: Photograph each stage of disassembly

11 Lab Notebook: 1-A: Explain how the shutter mechanism works (in your own words/sketches) - What causes the film advance after the capture button is pressed? - What prevents a double-exposure of the film? - How does the shutter mechanism operate? - How does the flash circuit physically operate? 1-B: Include photos at each stage of the disassembly

12 Experiment 2: Oscilloscope and FG setup: burst and trigger Goal: Calibrate instrumentation in order to measure flash Step 1: Generate square wave at 100 Hz, 5 VPP, 2.5 VDC offset, 5 ms pulse width Attach function generator to Channel 2Y on oscilloscope Push Wave Gen On oscilloscope, press Autoscale Step 1 Step 2 Step 2: On oscilloscope, press the 1 button (directly above input connector) Set trigger level to 4.0 VDC

13 Step 3: Step 4: Press Wave Gen Set frequency to pulse of 1 Hz On oscilloscope s Trigger section: Mode Normal.

14 Experiment 3: Camera flash circuit board installation Step 1: Step 2: Step 3: Scope Channel 1X: camera flash sensor Scope Channel 2Y: camera shutter sensor Scope or PC USB: camera USB connector Re-install battery Fit camera flash circuit board on the measurement board Push the camera flash circuit board button If necessary adjust Time/Div and Delay setting to get following display

15 Experiment 4: Reading measurements (with cursors) Goal: Use voltage and time cursors to measure flash times Step 1: Select Cursor. Set Cursor Mode to Manual Rotate knob to align cursors.

16 Step 2: Top wave: Flash Pulse Width (time flash remains lit) Adjust voltage cursors to measure max voltage difference (delta VF) Position V2 cursor at 0.5*delta VF Position time cursor T1 at start voltage step Position time cursor T2 at time where V2 intersects flash signal delta VF 0.5 delta VF Start of Voltage Step: T1 T2: Time V2 hits 0.5 delta VF Record Delta T = T2 T1. This is called the Flash Pulse Width

17 Step 3: Bottom wave: Shutter Pulse Width (time shutter remains open) Adjust voltage cursors to measure max voltage difference (delta VS) Position V2 cursor at 0.5*delta VS Position time cursor T1 on the rising part of shutter signal (V2) Position time cursor T2 on the falling part of shutter speed (V2) delta VS 0.5 delta VS T1 Rise point for V2 T2 Fall point for V2 Record Delta T = T2 T1. This is called the Shutter Pulse Width

18 Step 4: Leading Edge Offset (time between shutter-opening and flash-on) Place V1 cursor at 0.5 * delta VS for bottom wave (shutter signal) Place V2 cursor at 0.5* delta VF for top wave (shutter signal) Place T1 at V1 (rising) intersection Place T2 at V2 (rising) intersection V2: 0.5 delta VF V1: 0.5 delta VS T1 T2 Record Delta T = T2 T1. This is called the Leading Edge Offset

19 Step 5: Trailing Edge Offset (time between flash-off and shutter-close) Place V1 cursor at 0.5 * delta VS for bottom wave (shutter signal) Place V2 cursor at 0.5* delta VF for top wave (flash signal) Place T1 at V1 (falling) intersection Place T2 at V2 (falling) intersection V2: 0.5 delta VF V1: 0.5 delta VS T2 T1 Record Delta T = T2 T1. This is called the Trailing Edge Offset

20 Lab Notebook: We want 2 more trials of time data. Repeat Experiment 3 and 4 In your notebook, complete the table below with your values Trial Flash Pulse Width (ms) Shutter Pulse Width (ms) Leading Edge Offset (ms) Trailing Edge Offset (ms) Avg.

21 Discussion Points Take Home Points: Disposable camera has fixed features e.g. fixed shutter time Changes in shutter time will change photo s brightness Future labs aim to physically modify the plastic shutter These modifications will change shutter times and hence photos Source:

22 Film ASA (or iso) Ratings e.g. ISO 100, ISO 800 Low numbers: slower film = needs more light = longer exposures (slow shutter) High numbers: faster films = needs less light = shorter exposure (fast shutter) Slow film = sharper, detailed photos Fast film = higher contrast and grainy photos

23 Next Time: Week 03 Intro to Shutter Modification Bring camera: A disposable camera will be disassembled Search and read about disposable cameras Search how camera flashes work What are coil guns and tasers? What is a film ASA rating and how does this relate to shutter speed? Roughly calculate the shutter speed needed for a disposable camera